The prior art includes a variety of different types of material spreaders. Conventional lawn fertilizer spreaders include a hopper and a finger agitator rotated by spreader wheels. More closely related to the invention apparatus are material spreaders adapted for use in conjunction with the pouring and working of concrete spans. A number of companies make material spreaders for evenly spreading a layer of topping material on the wet surface of spans of concrete. The conventional spreader mounts one or more hoppers on a bridge which spans the width of the concrete and the hoppers are driven back and forth on the bridge to spread the material and the bridge which is mounted on wheels is manually moved lengthwise of the span after each pass of the hoppers. The hopper drive mechanism for a spreader of this type is typically powered either electrically or pneumatically which requires either power cables or air lines to be fed back and forth across the concrete span being worked. Such arrangements inherently require additional support structure and expense for the added structure, cables and air lines. U.S. Pat. No. 4,349,294 describes one such spreader. Trade literature distributed by K and G Equipment Design, Inc., of Yankton, South Dakota describes the "K and G" material spreader, another such spreader. Also, U.S. Pat. No. 4,411,554 describes a spreader having an electric drive and two spaced apart hoppers on a bridge.
With the foregoing in mind, the present applicant recognized that it would be desirable to provide an improved material spreader adapted for spreading a layer of material on the surface of a span of wet concrete and with a gasoline engine hydraulic system to drive the spreader so that neither power cables or air lines would be required. The achieving of a practical gasoline engine powered hydraulic system with an inherent ability to accommodate to either drive wheel or hopper agitator jamming has thus been one object of the invention.
With the object of achieving a practical gasoline engine powered hydraulic system which accommodates jamming as an object, applicant has discovered after a period of trial and experimentation with use of a hopper as a heat sink and with various gasoline engine powered hydraulic drive and hydraulic fluid-cooling arrangements that the means employed for dissipation of the heat generated in the oil being used to drive the spreader becomes a significant consideration. Prior attempts to use a hopper wall as a reservoir wall have not proven successful. Thus, another object of the invention has been that of achieving a practical gasoline engine powered hydraulic system for a bridge-supported material spreader with an improved hopper-reservoir arrangement to dissipate the heat accumulated in the oil used to drive the hydraulic elements of the system.
Another disadvantage of the prior art material spreaders of the type in which two spaced-apart hoppers are mounted on opposite sides of a bridge is that each hopper lays down a separate strip of material on each pass resulting in two laterally-spaced, narrow strips on each pass rather than one relatively wide strip of material on each pass. Thus, another object of the present invention is to achieve a material spreader with a hopper arrangement in which a relatively wide single span of material can be layed down on each pass of the spreader to avoid having to fill in between spaced-apart strips of material. Also, while driven paddle wheels in hoppers have been employed, it has not been known to drive the paddle wheel by an individual hydraulic motor as in the present invention so as to provide both independent paddle wheel spaced control and improved jamming action.
The foregoing and other objects will become apparent as the description proceeds.